When is the third book of the art by Clive Barker being released?

At least not until he has finished all the books of the Abarat series which last year he was saying he is getting closer to. He does plan to finish the series and has about 4 thick folders of notes and ideas for it. Check his official website 'Revelations' and click on the 'What's next' section to keep informed and see what he has said about this project in the past.